It was a strange booking.  Xabi Alonso stuck out a leg and caught Real Madrid’s onrushing defender, Pepe, but Javier Mascherano took the booking. This may have been for kicking the ball away, but the Argentinian seemed to be clearing it in case play didn’t stop. It didn’t look a bookable offense.

As Liverpool’s midfield janitor, Mascherano is no stranger to the yellow card. He’s so often the one in charge of breaking up mounting attacks, he’s become one of Liverpool’s most prolific tacklers. He occasionally gets the timing wrong, but refs don’t always believe him when he gets it right. Sometimes he’s booked for the perfect tackle just because his skill at dispossessing is, in a word, unbelievable.

So Mascherano had easily amassed four yellows in the Champions League by the time Frank de Bleekere booked him after Xabi’s challenge.

Now, Liverpool will have to face Chelsea on Wednesday without their janitor. They’ve beaten the Blues twice already, once without the help of Fernando Torres. But both victories over the London giants relied heavily on intense midfield pressure. Without Mascherano there to both reinforce the attackers and act as the first wave of defense, Liverpool’s job in the home leg of the quarter finals could be tougher than Chelsea’s visit to Anfield in February when the Reds won 2-0.

The likely cover for the suspended Argentinian will be Lucas Leiva.  The young Brazilian midfielder has not had the most convincing of seasons and his inexperience was painfully obvious when he gave up pivotal spot kicks in matches against Wigan and Everton, yet Rafael Benitez clearly has plenty of confidence in Lucas and feels the kid will step into his own.

We saw this faith in Lucas pay some dividends when Liverpool faced Manchester United without Xabi Alonso.  Alonso has been one of the Reds’ most influential players all season and taking on Man U at Old Trafford without him would seem a tall task indeed. But Lucas played one of his most convincing matches ever. Keeping his head well and orchastrating the short, crisp passes his is known for with consistency and vision. Liverpool won with Lucas covering for Alonso. But can Lucas offer anything like the solidity Javier Mascherano imposes on the midfield?

Chelsea boast a lot of power in their midfielders and attackers. When Mascherano returns for the second leg, they’ll have many frustrations trying to build chances out of the middle of the pitch, but they may think they can overpower the diminutive Lucas on Wednesday. Cleverness and short distribution are Lucas’s strengths when he plays well. But he’s small and can be bullied of the ball by players like Drogba and Lampard.

Chelsea will be eager to put away an away goal or two. Lucas will need to stand up to the pressure and help Liverpool’s defenders maintain a wall to make Chelsea’s attacks crumble. If Liverpool can keep a clean sheet at Anfield, they’ll feel confident they can cause another upset at Stamford Bridge on the 14th.

The task is a daunting one for the 21-year-old. But he called up the right mentality when asked to against United. Surely, if he’s going to raise his level of play further, a European quarter-final will be just the arena to inspire him.